diff --git a/apps/agent-worker/src/runtime/codex-adapter.ts b/apps/agent-worker/src/runtime/codex-adapter.ts
index 332e78d..4f93b5f 100644
--- a/apps/agent-worker/src/runtime/codex-adapter.ts
+++ b/apps/agent-worker/src/runtime/codex-adapter.ts
@@ -13,7 +13,11 @@ import {
   streamExecInContainer,
 } from './docker';
 import type { AdapterWorkspace } from './provider';
-import { codexModelArgs, providerEnvironment } from './provider';
+import {
+  codexModelArgs,
+  isCodexLoginProfile,
+  providerEnvironment,
+} from './provider';
 
 // Reused verbatim from the worker: normalize + pretty-print an auth JSON blob
 // before writing it with owner-only permissions.
@@ -41,6 +45,11 @@ export const createCodexAdapter: AdapterFactory = (deps) => {
   const execStream = deps?.execStream ?? streamExecInContainer;
 
   const prepareAuth = async (workspace: AdapterWorkspace) => {
+    // API-key profiles (e.g. OpenAI api_key) authenticate purely via
+    // OPENAI_API_KEY from providerEnvironment; only ChatGPT-login/JSON-snapshot
+    // profiles need a Codex `auth.json` on disk. Mirror the Claude adapter,
+    // which early-returns for non-OAuth profiles.
+    if (!isCodexLoginProfile(workspace.claim)) return;
     const secret = workspace.claim.aiProviderProfile?.secret;
     if (!secret) {
       throw new Error('Codex auth profile is missing auth.json contents.');
diff --git a/apps/agent-worker/tests/unit/codex-adapter.test.ts b/apps/agent-worker/tests/unit/codex-adapter.test.ts
index f1600a8..a5b7761 100644
--- a/apps/agent-worker/tests/unit/codex-adapter.test.ts
+++ b/apps/agent-worker/tests/unit/codex-adapter.test.ts
@@ -1,9 +1,24 @@
-import { describe, expect, test, vi } from 'vitest';
+import { mkdir, mkdtemp, readFile, rm, stat } from 'node:fs/promises';
+import os from 'node:os';
+import path from 'node:path';
+
+import { afterEach, describe, expect, test, vi } from 'vitest';
 
 import type { NormalizedAgentEvent } from '../../src/agent-events';
 import type { ExecStreamFn } from '../../src/runtime/agent-runtime';
 import type { AdapterWorkspace, Claim } from '../../src/runtime/provider';
 
+const tempDirs: string[] = [];
+
+const pathExists = async (filePath: string): Promise<boolean> => {
+  try {
+    await stat(filePath);
+    return true;
+  } catch {
+    return false;
+  }
+};
+
 const loadAdapter = async () => {
   process.env.SPOON_WORKER_TOKEN = 'test-worker-token';
   process.env.GITHUB_APP_ID = '123';
@@ -51,7 +66,88 @@ const makeWorkspace = (): AdapterWorkspace => ({
   runtime: 'codex',
 });
 
+const makeAuthWorkspace = async (
+  profile: Record<string, unknown>,
+): Promise<AdapterWorkspace> => {
+  const workdir = await mkdtemp(path.join(os.tmpdir(), 'spoon-codex-auth-'));
+  tempDirs.push(workdir);
+  const repoDir = path.join(workdir, 'Code', 'spoon');
+  await mkdir(repoDir, { recursive: true });
+  return {
+    ...makeWorkspace(),
+    claim: { ...claim, aiProviderProfile: profile } as unknown as Claim,
+    workdir,
+    homeDir: workdir,
+    repoDir,
+  };
+};
+
 describe('CodexAdapter', () => {
+  afterEach(async () => {
+    await Promise.all(
+      tempDirs.map((dir) => rm(dir, { force: true, recursive: true })),
+    );
+    tempDirs.length = 0;
+  });
+
+  test('prepareAuth skips auth.json for an api_key profile', async () => {
+    const { createCodexAdapter } = await loadAdapter();
+    const adapter = createCodexAdapter();
+    const workspace = await makeAuthWorkspace({
+      id: 'p',
+      name: 'OpenAI',
+      provider: 'openai',
+      authType: 'api_key',
+      model: 'gpt-5',
+      // A raw API key, which is deliberately NOT valid JSON.
+      secret: 'sk-test',
+    });
+
+    await expect(adapter.prepareAuth?.(workspace)).resolves.toBeUndefined();
+
+    const codexAuthPath = path.join(workspace.workdir, '.codex', 'auth.json');
+    const openCodeAuthPath = path.join(
+      workspace.workdir,
+      '.local',
+      'share',
+      'opencode',
+      'auth.json',
+    );
+    await expect(pathExists(codexAuthPath)).resolves.toBe(false);
+    await expect(pathExists(openCodeAuthPath)).resolves.toBe(false);
+  });
+
+  test('prepareAuth writes auth.json for a ChatGPT-login profile', async () => {
+    const { createCodexAdapter } = await loadAdapter();
+    const adapter = createCodexAdapter();
+    const secret = JSON.stringify({ tokens: { access: 'abc' } });
+    const workspace = await makeAuthWorkspace({
+      id: 'p',
+      name: 'Codex',
+      provider: 'opencode_openai_login',
+      authType: 'opencode_auth_json',
+      model: 'gpt-5',
+      secret,
+    });
+
+    await adapter.prepareAuth?.(workspace);
+
+    const codexAuthPath = path.join(workspace.workdir, '.codex', 'auth.json');
+    await expect(readFile(codexAuthPath, 'utf8')).resolves.toBe(
+      `${JSON.stringify(JSON.parse(secret), null, 2)}\n`,
+    );
+    const openCodeAuthPath = path.join(
+      workspace.workdir,
+      '.local',
+      'share',
+      'opencode',
+      'auth.json',
+    );
+    await expect(readFile(openCodeAuthPath, 'utf8')).resolves.toBe(
+      `${JSON.stringify(JSON.parse(secret), null, 2)}\n`,
+    );
+  });
+
   test('streams normalized events and marks the turn via buildMarkedCommand', async () => {
     const { createCodexAdapter } = await loadAdapter();
     const captured: unknown[] = [];